The use of raw materials cultivated in Mozambique in the feeding of growing chickens
E Wethli* and C Paris**
*NPI, c/o Ukulinga Research Farm, Box 101188, Scottsville 3209, South
**Ministry of Agriculture, Maputo, Mozambique.
An experiment was carried out to determine whether maize, sorghum, sesame seeds, cowpeas and sweet potato leaves, all produced in many areas of Mozambique, could, together with bonemeal and salt, provide a simple diet for growing chickens.
The trial consisted of five treatments: a commercial diet acting as control, and four diets made up of local ingredients (two with and two without vitamin/mineral premix; the two without were fed sweet potato leaves); the last of these treatments was a "free choice" of the different raw materials. Starting at eight weeks of age, these diets were fed to 530 chickens consisting of roughly equal numbers of the breeds New Hampshire, Barred Plymouth Rock and the cross White Cornish x New Hampshire, which acted as replicates. The experiment continued over an eight-week period.
The main result was that a diet formulated using these locally available ingredients, without a premix but receiving green leaves, produced a weight gain that was about 20% lower than that attained by a commercial diet, with about 15% inferior feed conversion, and a similar mortality. This is discussed in the light of the relative unavailability of commercial poultry feed in most rural agricultural production co-operatives.
KEY WORDS: Poultry, rural, local feeds, choice feeding, growth.
Immediately after Independence in 1975, the Mozambican government defined as a priority the development of livestock production in the rural Family Sector. A large part of the raw materials used in balanced commercial feed for monogastric animals had to be imported. Besides the obvious foreign exchange drain, in the remote rural areas there were enormous transport problems so that even local ingredients such as bran and the oilseed cakes were often unavailable. Hence, it was clear that unless locally available feeds could be used, there was little possibility of improving the nutrition of rural poultry.
The objective of the present study was to determine what level of production was possible with local feeds of low nutritive value, using no animal protein; and whether this production was economically sustainable. In the literature there is a scarcity of relevant information. Besides the work of Milligan (1973) and Sevenhuysen (1976), most experiments simply deal with the substitution of one ingredient by another, but within the context of an already well-balanced diet. They provide no answers to the questions: how can we feed chickens and ducks in the situation where animal protein, high-quality oilseed cakes, vitamin and mineral premixes are scarce; and is there no way of improving the traditional system where the birds search for their own feed (and maintain extremely low levels of production).
Materials and methods
The experiment was carried out in January, 1979 over an eight-week period. The mean daily temperature during this period was 28.2°C, with a range in maximum temperature of 29 to 43°C and a minimum of 15 to 26 ?C.
|Table 1: Formulae and analyses of the experimental diets|
|Sweet potato leaves||-||-||+|
|N x 6.25 (g/kg)||170||167||164||165|
|Met + Cys(g/kg)||6.1||4.8||5.3||5.3|
The crops studied in this trial, all commonly encountered in Mozambique, were maize (Zea mays), sorghum (Sorghum vulgare), sesame (Sesamum indicum), cowpea (Vigna unguiculata), and the leaves of sweet potato (Ipomoea batatas). Sesame and cowpea were chosen because of their relatively high contents of methionine and lysine, respectively. There is no mention in the literature of any marked toxicity with the use of raw cowpeas in animal feeding, although the presence of a trypsin inhibitor has been reported.
The experimental plan consisted of five treatments with three replications each. In order to obtain some information on breed effect, each replication consisted of a different breed, namely, New Hampshire, Barred Plymouth Rock and the White Cornish Game x New Hampshire cross. The formulae of the five diets together with the calculated compositions of the main nutrients are given in Table 1. The determined proximate analyses of these raw materials are in Annex 1.
It is important to note that "sesame" refers to the complete seed and not the deoiled cake. The control treatment was the normal commercial grower diet used for layer-type chickens from about six to 15 weeks of age. In the formulation of Local1, Local2 and Local3, an attempt was made to keep these as simple as possible while trying to satisfy the minimum requirements for methionine and lysine. Cowpeas are much cheaper than sesame, and with its relatively high lysine level, it should complement maize and sorghum. Thus in Local1 the level of cowpea was increased at the expense of sesame. This might also give an indication whether higher levels of this legume are toxic.
The contents of calcium, available phosphorus and salt in Local1-3 were maintained at levels considered adequate for the type and age of bird. A commercial vitamin/mineral premix was added to the control and Local 1 and Local2. No premix was included in Local3, but the birds on this treatment were given fresh green leaves of sweet potato, in order to see whether the leaves could compensate for the lack of premix. Because they were easily available at the time sweet potato leaves were used (it is also common knowledge that chickens readily eat these leaves, and according to Rojoa et al (1981), sweet potato leaves have a high nutrient value as animal feed. From the literature it would seem that chickens can consume up to 50 to 85 g of palatable fresh leaves per day. An amount of green leaves (with petiole but excluding stem) to provide an average daily intake of at least 50 g per bird per day was weighed out on the first day of the trial and a similar quantity was given on subsequent days. Half this amount was fed in the mornings and half in the afternoons. Owing to practical difficulties no attempt was made to measure the actual consumption of leaves.
The Choice treatment was of an empirical nature: the chickens were given a free-choice of maize, sorghum, sesame seeds and cowpeas, provided in separate but similar hoppers, in order to see what "diet" they themselves would select. The birds on this treatment also received leaves twice a day. Bonemeal and salt were added to the maize on the assumption that the maize would constitute approximately 25% of the diet chosen. Unfortunately, during the first four weeks of the trial the chickens ate almost exclusively maize, so the treatment was changed, the maize being entirely removed. The birds then consumed mainly sorghum during the next two weeks. Thus, this was also removed, and during the last two weeks they only had the sesame and cowpeas available. (After the maize was taken away, bonemeal and salt were provided in separate containers.)
The diets were mixed once for the duration of the experiment (eight weeks). The sesame was left unground, while the other ingredients were passed through a hammer mill. All diets were fed ad libitum.
From day-old, birds of the three breeds were reared on the floor and received a balanced commercial starter diet. They were vaccinated against Newcastle Disease, and, just before the start of the trial, they were given a preventative dose of coccidiostat. At eight weeks of age 530 chickens were weighed and distributed at random, with the proviso that an attempt was made to have an equal number of males and females in each division, among the 15 divisions of an open-sided experimental house. During the eight weeks of the trial, all the birds were weighed and feed consumption determined at two-weekly intervals. At the final weighing the sexes were weighed separately. All mortality was registered, and all dead birds were sent to the National Institute of Veterinary Research for autopsy. An analysis of variance test was applied to the results. In the case of mortality, the percentages were first transformed with an arcsine angular transformation.
Except for the case of the Choice treatment, already mentioned, the main trends in performance at the two-weekly weighings, and of the males and females at the 16-week weighing were essentially similar. There were also no statistically significant differences among the three breeds. Thus, this report only considers the results of the complete eight to 16-week period of the trial, and of the three breeds and males and females together.
The mean body weights, feed consumption (excluding leaves), feed efficiency, mortality and economic index (cost of feed/kg wt gain) are presented in Table 2.
The control birds had significantly heavier final weights than those on any other treatment. There were no significant differences in either final body weight or weight gain among treatments Local 1-3. The 16-week weight of these latter treatments was about 15% lower and the weight gain about 28% lower than that of the control. The birds on the Choice treatment E had a significantly lower final weight and weight gain than those on the other treatments.
|Table 2: Performance data (8-16 weeks)|
|Feed int (g)||5155a||4734a||5303a||4684a||2904b|
abc Differences between values with the same letter are not statistically significant at the 5% level of probability.
There were no significant differences in feed consumption and feed efficiency among all treatments with mixed diets, although the control tended to be the best. The feed intake, but not the efficiency, of the Choice treatment was significantly lower than that of the other treatments. The intake of raw materials (excluding leaves) of the Choice treatment over the eight weeks of the trial was (g): maize 1274, sorghum 945, sesame 81, cowpeas 420, bonemeal 159 g and salt 25.
No clear pattern of mortality attributable to treatment emerged. (The absence of mortality with the control diet was unusual as normally 2-3% mortality would have been expected over the period of the trial). In spite of the low growth rate, there was not a correspondingly high mortality with the choice treatment.
In trying to assess the economics of this experiment, a difficulty arises as to what price to allocate to the raw materials used in the diets other than the control. The producer price rather than the market price was chosen as it was assumed that the poultry farmer would be producing crops specifically to feed his/her birds. However, the market price of the control diet was used. The calculations employed the prevailing prices in Mozambique at the time. The economic indices in Table 2 are given simply to provide some indication of the relative economic worth of these diets (another shortcoming is that no cost for the leaves consumed is included for Local3 and Choice treatments. It may be seen that, except in the case of Local2, the estimate of economic return for the experimental diets is not markedly inferior to that of the control, and this is especially important when one considers that the cost of the control diet has a very high foreign exchange component. It is important to note that the cost of liveweight gain was lowest on the "semi" free choice system as the birds ate most of the lowcost "cowpeas".
The observed growth rates were quite reasonable, particularly when the dietary quality, breeds and the high ambient temperature experienced during the trial are taken into consideration. The feed intakes are a bit higher than expected for birds of this age.
The chickens that received the Local3 diet, using only locally available raw materials, grew about 20% slower than those fed the commercial control diet, with a 15% poorer feed conversion. Given that commercial feed was virtually unobtainable in most rural areas in Mozambique, these levels of production seem quite satisfactory, and are appreciably better than those found under normal traditional (scavenging) family sector conditions (although, of course, the costs are also greater).
The low cost of gain on the "choice" treatment is an interesting observation, nevertheless interpretation is confounded by the decision to stop offering maize or sorghum midway through the trial.
It would be useful to look at the effects of the present raw materials over a longer period, and to determine the actual nutritive contribution of the green leaves.
Other interesting topics that could be looked into include the use of whole sunflower seeds, other beans such as pigeon pea, other greenfeed (especially legumes), possible sources of animal protein (such as insects, larvae and worms) which would facilitate the feeding of chicks.
Simple treatments to improve the nutritive value of raw materials containing toxic substances should also be investigated.
Milligan J L 1973Poultry feeds and feeding for Peruvian Selva tribes. Poultry Science 52: 2065 (Abstract). [The full article, kindly supplied by the author, was consulted]
Rojoa, Naidu & Owadally 1981 Yield potential of six sweet potato varieties as fodder. Revue Agricole et Sucriere de l'Ile Maurice
Sevenhuysen G P 1976 An analysis of selected aspects of applied nutrition fieldwork in Ethiopia relevant to developing countries. A thesis submitted for the degree of Doctor of Philosophy
|Annex 1: Determined analysis (in g/kg) of the raw materials|
|Moisture||N x 6.25||CF||EE|
|Sweet potato leaves||817||25.5||22.0||7.6|
(Received 1 April 1995)